1. Field of the Invention
The present invention relates to a three-dimensional measuring device and three-dimensional measuring method for non-contact measuring of an object shape by illuminating an object with light.
2. Description of the Related Art
Three-dimensional measuring devices of the non-contact type commonly referred to as rangefinders are used for data input to CG systems and CAD systems, somatometry, robot visual recognition and the like because it is possible to measure at high speed compared to contact type devices. The optical slit projection method (also referred to as the light section method) is known as suitable measuring method for rangefinders. This method produces a three-dimensional image (distance image) by optically scanning an object, and is one type of active measuring method for imaging an object illuminated by a specific light. The three-dimensional image is a collection of pixels representing the three-dimensional positions of a plurality of parts on an object. In the optical slit projection method the section of a linear slit light is used as the detection light.
FIGS. 46a, 46b, 46c, and 46d briefly show the optical slit projection method, and FIGS. 47a, 47b, and 47c illustrate the principles of measurement via the optical slit projection method.
A section of object Q serving as a measurement subject is illuminated by a thin band-like slit light U, and, the light reflected from the object Q impinges, for example, the imaging surface S2 of a two-dimensional image sensor (FIG. 46a). If the illuminated portion of object Q is flat, the sensed image (slit image) is a straight line (FIG. 46b). If the illuminated portion is uneven, the straight line becomes curved and step-like (FIG. 46c). That is, the magnitude of the distance between the measuring device and the object Q is reflected at the incident position of the reflected light on imaging surface S2 (FIG. 46d). Three-dimensional position sampling can be accomplished by scanning the object surface on a range viewed from the light reception side by deflecting the slit light U perpendicular to the length direction. The number of points of this sampling is dependent on the number of pixels of the image sensor.
In FIGS. 47a, 47b, and 47c, the light emitting system and light receiving system are positioned such that the base line AO connecting the origin A of the projection light and the principal point of the light reception lens is perpendicular to the optical axis of received light. The principal point of the lens is a point on the receiving optical; axis separated from the sensing surface S2 only by the so-called image distance b when the image of an object at infinite distance is formed on imaging surface S2. The image distance b is the sum of the focal length f of the light receiving system and the amount of lens extension for focusing adjustment.
The principal point O is the origin of the three-dimensional orthogonal coordinates. The light reception axis is the Z axis, the base AO is the Y axis, and the slit light length direction is the X axis. When the slit light U illuminates point P (X,Y,Z) on the object, and the angle of the projection axis and projection reference plane (projection plane parallel to the light reception axis) is designated xcex8a, and the light reception angle is designated xcex8p, the coordinates Z of point P are expressed by the equation below.
Base line length L=L1+L2=Ztan xcex8a+Ztan xcex8p
∴Z=L/(tan xcex8a+tan xcex8p)
The light receiving angle xcex8p is the angle formed by a line connecting point P and principal point O, and the plane including the light reception axis (i.e., light reception axis plane).
Since the imaging magnification xcex2=b/Z, when the distance between the center of imaging surface S2 and the light reception pixels in the x direction is designated xp and the distance in the Y direction is designated yp (refer to FIG. 47a), the coordinates X,Y of point P are expressed by the equations below.
xe2x80x83X=xp/xcex2
Y=yp/xcex2
The angle xcex8a is unconditionally determined by the angular speed of deflection of slight light U. The light reception angle xcex8p is calculated from the relationship: tan xcex8p=b/yp. That is, the three-dimensional position of point P can be determined based on the angle xcex8a by measuring the position (xp,yp) on the imaging surface S2
When the light reception system is provided with a zoom lens unit as shown in FIG. 47c, the principal point O becomes the posterior side principal point Hxe2x80x2. When the distance between the posterior side principal point Hxe2x80x2 and the anterior side principal point H is designated M, the Z coordinate of point P is expressed by the equation below.
L=L1+L2=Ztanxcex8a+(Zxe2x88x92M)tanxcex8p
∴Z=(L+Mtanxcex8p)/(tanxcex8a+tanxcex8p)
When an image sensing means is used which comprises an imaging surface S2 having a finite number of pixels as in, for example, a CCD sensor, in the measurement performed via the previously described slit light projection method, the measurement resolving power is dependent on the pixel pitch of the image sensing means. That is, the resolving power can be increased by setting the slit light U so that the width of said slit light U in the Y direction (scanning direction) impinges a plurality f pixels on the imaging surface S2.
FIG. 48 illustrates the principles of this measurement method.
When the reflectivity of the illuminated portion of the object is assumed to be uniform, the intensity of the received light is a normal distribution expanding on the Y direction. If the effective intensity range of this normal distribution is a plurality of pixels, the maximum intensity position (i.e., barycenter) can be measured in units under the pixel pitch by interpolation of the amount of light received by each pixel g. This interpolation fits the normal distribution to the amount of light received by each pixel. The X, Y, and Z coordinates are determined based on the barycenter determined by the aforesaid calculation. If this method is used, the actual resolving power is xe2x85x9 to {fraction (1/10)} pixels.
When measuring via the slit light projection method, the person doing the measurement determine the position and direction of the rangefinder, and sets the scanning range (image sensing range) of the object Q via a zoom operation as necessary. It is useful to display a monitor image of the sensed object Q at the same field angle as the scanning range to easily accomplish the aforesaid framing operation. In three-dimensional CG, for example, color information of the object Q as well as measurement data expressing the shape of the object Q are often required.
Conventional rangefinders have a spectral means (e.g., dichroic mirror) for separating the light transmitted through the light-receiving lens system into slit light and environmental light, and are constructed so as to produce a color monitor image at the same field angle as the distance information by directing the environmental light to a color image sensing means separate from the image sensing means used for measurement (refer to Japanese Unexamined Patent Application No. SHO 7-74536).
If a dichroic mirror is used as the aforesaid spectral means, the entering light can be separated by wavelength virtually without decreasing the amount of light.
In practice, however, there are no dichroic mirrors which have ideal wavelength selectivity for reflection or transmission of only the slit light. Therefore, conventionally a disadvantage exists insofar as the environmental light greatly affects measurements because light of a comparatively broad wavelength range including the slit light wavelength enters the image sensing means.
In order to increase the resolving power, the width (i.e., length in the scanning direction) of the slit light may be increased by stages of projection light by setting the width of the slit light of the image imaging surface S2 to a plurality of pixels. In so doing, the distribution of the intensity of the received light doe snot form a normal distribution when the illuminated portion (point P) is the border of an object color because the width in the Y direction of the slit light broadens on the object Q, thereby increasing measurement error.
In conventional devices, the projection light conditions are set such that the slit width is as narrow as possible on the object Q, and the width of the slit light U is broadened then impinges the imaging surface S2 by means of a filter or the like in the light reception system.
The narrowing of the width of slit light U is optically limited, however. The illumination range (slit width) on object Q broadens as the distance increases from the starting point A of the projection light. Accordingly, conventional devices are disadvantageous inasmuch as the measurement distance (distance between the measuring device and the object Q) at which measurement of a specific precision is possible is short regardless of the distribution of the reflectivity of the object Q.
In conventional devices, the mutual positional relationship between the light projecting device comprising the projection system and the device comprising the light receiving system is fixed, such that the constructions do not allow adjustment of the respective optical axes, not center axis line and scan direction.
Therefore, in conventional three-dimensional input cameras, twisting occurs among the mutual optical axes, center line axes, and scanning direction of the light projection device and light receiving device, such that said axes are not in the same plane and errors arise in the mutual positional relationships. These errors also occur in three-dimensional input cameras using a zoom lens, but these errors can be corrected with relatively easily based on calculations using correction data obtained by imaging.
When a three-dimensional input camera is provided with a zoom lens, however, correction data differ in accordance with the amount of operation and movement of the zoom lens, such that there are extremely large amounts of correction data and individual parameters which make it impossible to perform simple calculations due to the extreme complexity of error correction, and require a great deal of time for the calculation process. Thus, a further disadvantage is the inclusion of many errors in the input data, which make it impossible to perform accurate calculations.
Although the framing which determines the scanning range of the object Q can be performed with a high degree of freedom by providing a zooming mechanism in the rangefinder as in conventional devices, disadvantages arise inasmuch as when zooming the principal point of the light receiving system is moved on the optical axis and causes errors to occur in the triangular measurement.
Furthermore, when the light receiving system is provided with w zooming function, the imaging field angle changes due to said zooming. Therefore, the width of the slit light on the projection side must be adjusted in accordance with the zooming performed on the light receiving side so as to introduce the maximum width slit light U onto the imaging surface S2.
Conventional devices are provided with a passive type distance sensor as a rangefinder which allows variable imaging distances depending on mode of use. The range measurement result is used in autofocusing (AF), and setting the projection light intensity.
The aforesaid passive type distance sensor produce large errors due to lens focal length, subject contrast distribution and the like. In contrast, rangefinders are capable of active type precision range measurement using a measurement-specific optical system. Measurement conditions including the autofocus lens position, and detection light projection angle range can be finely adjusted to increase measurement precision and improve measurement resolving power. Furthermore, in the actual projection of the detection light and measurement of the received light, passive type optical distance measurement and ultrasonic distance measurement differ such that distance information and reflectivity information of the object surface can be obtained as measurement environmental information. If reflectivity information is used, it is possible to set more suitable light receiving conditions (e.g., amount of projection light, light reception sensitivity and the like) compared to simply changing set values in accordance with distance.
When optical scanning identical to the measurement time is accomplished as a preliminary measurement before the main measurement, however, the specific time of the operation combining the preliminary measurement and the measurement following thereafter, i.e., the measurement time of one cycle, becomes longer. When the calculation of the preliminary measurement is performed relative to the sampling points of the entirety of the image sensing range, the amount of said calculation is extensive, such that the specific time of the preliminary measurement becomes longer.
In conventional devices, a passive type distance sensor is provided in a rangefinder capable of variable imaging distances according to the mode of use. The distance measurement result is used to set the autofocus (AF) and projection light intensity.
Even when the projection light intensity is adjusted in accordance with the distance measurement result, the amount of received light of the detection light is reduced to less than a lower limit when the reflectivity of the object surface is too low, such that suitable measurement results cannot be obtained. Thus, suitable final measurement results cannot be obtained when the amount of received light exceeds a lower limit due to positive reflectivity of the object surface and the introduction of environmental light. Furthermore, the measurement error increases when measurement distance range set based on the measurement result is outside possible measurement.
Conventionally, when measurement parameters such as reflectivity, distance-to-object, measurement range and the like are unsuitably set, a user will invariably judge that suitable measurement has been accomplished the measurement operation is completed regardless of whether or not a suitable measurement result can actually be obtained.
An object of the present invention is to provide an improved three-dimensional measuring device and three-dimensional measuring method.
Another object of the present invention i to provide a spectral device capable of producing a monitor image having the same field angle as the distance image and capable of realizing three-dimensional measurement only slightly influenced by environmental light, and a three-dimensional measuring device for use in said spectral device.
Another object of the present invention is to realize a three-dimensional measuring device which allows a great degree of freedom in setting measurement distances, and is capable of high precision measurement at high resolving power when the reflectivity of an object is nonuniform with effectiveness similar to when said reflectivity is uniform.
Yet another object of the present invention is to provide a three-dimensional input camera capable of eliminating error in the positional relationship between the light projecting device and the light receiving device, and capable of accurate measurement with minimal error when a zoom lens is installed.
A further object of the present invention is to provide a measuring device having excellent practicality with minimal measurement error and minimal restrictions on imaging position setting.
A still further object of the present invention is to provide a compact light projection device capable of emitting distortionless slit light and which allows adjustment of the slit width, and a three-dimensional measuring device utilizing said light projection device.
An even further object of the present invention is to realize high-speed and high-precision three-dimensional measurement by effectively measuring the measurement environment relating to the measurement parameter settings.
Yet another object of the present invention is to provide a three-dimensional measuring device capable of performing suitable operation by allowing a user to confirm the unsuitability of measurement conditions before and after measurement.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which illuminates an object with light or specific wavelength; and
an optical reception system which receives light reflected by the object, said optical reception system including;
a spectral means for separating the light of a predetermined wavelength range including said specific wavelength into light of another wavelength range, and
a filtering means provided on the optical path of the light of said predetermined wavelength range separated by said spectral means, said filtering means blocking from among the light within said predetermined wavelength range, light which is of a wavelength longer than said specific wavelength and light which is of a wavelength shorter than said specific wavelength.
These objects and other objects are achieved by providing a three-dimensional measuring method comprising steps of:
illuminating an object with light of specific wavelength;
dividing the light reflected by the object into a first light of a wavelength range including said specific wavelength and a second light of another wavelength range;
cutting from the divided first light, light which is of a wavelength longer than said specific wavelength and light which is of a wavelength shorter than said specific wavelength, to obtain the light of the specific wavelength; and
sensing said obtained light of the specific wavelength for three-dimensional measuring.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which sequentially illuminates an object with light at variable illumination angles;
an image sensor which periodically samples the light reflected by the object synchronously with the variation of illumination angle of said optical projection system; and
a first calculation means for calculating the illumination timing of maximum light reception by said image sensor based on a maximum sampling value obtained by said image sensor, and the sampling values of the sampling cycles one cycle before and one cycle after the sampling cycle which obtained said maximum value for measuring a three-dimensional position of the object.
These objects and other objects are achieved by providing a three-dimensional measuring method comprising steps of:
sequentially illuminating an object with light at variable illumination angles;
receiving the light reflected by the object on an image sensor;
periodically sampling the received light synchronously with the variation of illumination angle by the image sensor; and
calculating the illumination timing of maximum light reception by said image sensor based on a maximum sampling value obtained by said image sensor, and the sampling values of the sampling cycles one cycle before and one cycle after the sampling cycle which obtained said maximum value for measuring a three-dimensional position of the object.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which illuminates an object;
an optical reception system which receives light reflected by the object illuminated by said optical projection system; and
an adjustment mechanism for adjusting the relative positions of said optical projection system and said optical reception system, said adjustment mechanism maintaining said projection system and said reception system so as to be relatively rotatable on a first rotational axis along the optical axis of said reception system and a second rotational axis perpendicular to said first rotational axis.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which illuminates an object with light beam;
an image sensor which outputs image signals corresponding to the amount of light impinging the image sensing surface;
an optical reception system which forms an optical image of the object on the image sensing surface of said image sensor;
a detection means for detecting the principal point position of said optical reception means; and
a calculation means for calculating a three-dimensional position of the object based on the principal point position detected by said detection means and the image signals of the object obtained by said image sensor.
These objects and other objects are achieved by providing a three-dimensional measuring method comprising steps of:
illuminating an object with light beam;
forming an optical image of the object on an image sensing surface of an image sensor by an optical reception system;
outputting image signals corresponding to the amount of light impinging the image sensing surface;
detecting the principal point position of said optical reception system; and
calculating a three-dimensional position of the object based on the detected principal point position and the image signals.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which illuminates an object with light;
an image sensor which outputs image signals corresponding to the amount of light impinging the image sensing surface;
an optical reception system for forming an optical image of the object on the image sensing surface of said image sensor via light emitted said optical projection system and reflected by the object;
a preliminary measurement control means for executing a preliminary measurement by making said optical projection system and said image sensor operate prior to an actual three-dimensional measurement to obtain information on the distance to the object based on the image signals of the object imaged by said image sensor; and
a actual measurement control means for setting a measurement condition in accordance with the distance information obtained by said preliminary measurement and for executing the actual measurement by making said optical projection system and said image sensor operate under the set measurement condition to actually measure the three-dimensional position of the object.
These objects and other objects are achieved by providing a three-dimensional measuring method comprising steps of:
illuminating an object with light;
forming an optical image of the illuminated object on an image sensing surface of an image sensor;
outputting image signals corresponding to the amount of light impinging the image sensing surface;
obtaining information on the distance to the object based on the reflection light from said object imaged by said image sensor prior to an actual measurement of the three-dimensional position of the object;
setting a measurement condition in accordance with the obtained distance information; and
executing the actual measurement of the three-dimensional position of the object under said set measurement condition.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which projects light on an object with varying the projection angle within a predetermined range of projection angles;
an image sensor which receives light reflected from the object illuminated by said projection system and generating image signals of the object;
a preliminary measurement control means for executing a preliminary measurement by making said optical projection system operate within only a part of the predetermined projection angle range prior to actual three-dimensional position measurement and by driving said image sensor to generate the image signals; and
a actual measurement control means for setting a measurement condition in accordance with the image signals obtained by said preliminary measurement and for controlling said optical projection system and said image sensor to execute the actual measurement under the set measurement condition.
These objects and other objects are achieved by providing a three-dimensional measuring method comprising steps of:
executing a preliminary measurement which includes steps of projecting light on an object with varying the projection angle within a narrow predetermined range of projection angles, sensing the light reflected from the illuminated object, and generating image signals of the object;
setting a measurement condition in accordance with the image signals obtained by said sensing step; and
executing, under said measurement condition set by said setting step, an actual three-dimensional measurement which includes steps of projecting light on the object with varying the projection angle within a wide predetermined range of projection angles, sensing the light reflected from the illuminated object, and generating image signals of the object.
These objects and other objects are achieved by providing a three-dimensional measuring device comprising:
an optical projection system which projects light on an object with varying the projection angle;
an image sensor which receives light reflected from the object illuminated by said projection system and generating image signals of the object;
a preliminary measurement control means for executing a preliminary measurement prior to an actual measurement by making said optical projection system and said image sensor operate;
a setting means for setting a measurement condition for the actual measurement in accordance with a part of the image signals obtained by said preliminary measurement;
an actual measurement control means for executing the actual measurement under said set measurement condition by making said optical projection system and said image sensor operate; and
a calculating means for calculating three-dimensional positions of the object in accordance with entire image signals obtained by said actual measurement.
These objects and other objects are achieved by providing a three-dimensional measuring device which projects light on an object and senses the light reflected by said object under variable measurement conditions to obtain three-dimensional positions of the object, said three-dimensional measuring method comprising;
a judging means for judging whether said measurement conditions are acceptable or not; and
a warning means for warning if said judging means judges that said measurement conditions are not acceptable.
These objects and other objects are achieved by providing a three-dimensional measuring device which projects light on an object and senses the light reflected by said object under variable measurement conditions to obtain information related to three-dimensional positions of the object, said three-dimensional measuring method comprising;
a display on which displays the obtained information;
a judging means for judging the obtained information are acceptable or not; and
a control means which displays the unacceptable information in different shape from the acceptable information on said display.
These objects and other objects are achieved by providing a optical system used in three-dimensional measurement apparatus which measures three-dimensional positions of an object, said optical system comprising an optical projection device which includes:
a light source which emits light beam therefrom;
a variator which is provided on a path of said light beam emitted by light source and varies diameter of the light beam;
an expander which is provided on a path of the light beam varied by said variator and expand the light beam in one direction to form a slit light beam; and
a deflector which deflects said slit light beam formed by said expander.